i have done that. this happens regardless of tube

I'm confused now. The amp came with two 6CA7 tubes. You bought two EL34 as replacements.

Maybe you got a bad tube.
Time to get another pair.

http://www.thetubestore.com/EL34-6CA7-KT77-Tube-Reviews

 

And idle current of 38 ma in one and 34 ma in the other, I would think the filaments are ok.
A ~ 10% difference.
Most tube circuits have wide tolerances. It was just a drive by comment on the tube glow.........I haven't been keeping up on your project or mods.

Yeah. I am just confused becuase I have never seen anything like this before

 

I'm confused now. The amp came with two 6CA7 tubes. You bought two EL34 as replacements.

Maybe you got a bad tube.
Time to get another pair.

http://www.thetubestore.com/EL34-6CA7-KT77-Tube-Reviews

The amplifier came with 2 6ca7's it had the difference in filament glow, so i had el34's laying around that i know work, i put those in, still weird glow issue

 

Why don't you measure the ac voltage across the filaments?

 

Why don't you measure the ac voltage across the filaments?

across pin 2 and 7?

 

I would have though that if the problem was circuit related, the effect would stay with the socket and not move with the tube.
Anyhow, you may want to check or replace the two 270kΩ grid bias resistors.

 

I would have though that if the problem was circuit related, the effect would stay with the socket and not move with the tube.
Anyhow, you may want to check or replace the two 270kΩ grid bias resistors.

It does stay with the socket, whatever is in that socket has the lesser glow.

Just checked the resistors. they are good

 

It does stay with the socket, whatever is in that socket has the lesser glow.

Shucks. Now you say that. That is a whole new scenario now. 25 wasted posts.
I'm outta here.

 

Shucks. Now you say that. That is a whole new scenario now.
I'm outta here.

I thought that was clear from the beginning. Despite the tube, whatever in that socket has lower filament glow

 

I don't know......I don't have a data sheet. I wouldn't suspect the filaments for the un-even current.

But you can verify the filaments by measuring the voltage across them and the current thru them. It's easy to check because of point to point wiring and alligator clips.

But before you do that, check for a grid bias difference. That's probably what's causing the different in plate current.

 

I don't know......I don't have a data sheet. I wouldn't suspect the filaments for the un-even current.

But you can verify the filaments by measuring the voltage across them and the current thru them. It's easy to check because of point to point wiring and alligator clips.

But before you do that, check for a grid bias difference. That's probably what's causing the different in plate current.

so the two 270k resistors

 

Just measure the grid voltages.

 

Just measure the grid voltages.

Will do. Going to post back tomorrow after I measure it. why would the filaments do that anyway? any ideas?

 

Because the inside of the tube has been getter blasted........graffitified.

 

Because the inside of the tube has been getter blasted........graffitified.

But they are brand new and it happens despite the tubes. Whatever is in that socket has the issue

 

okay. Well. I fixed it. replacing the coupling caps somehow did it. Anyway. I now want to get onto shaping the tone. heres a schematic of the amplifier I am trying to mimic in tone. here is mine. The preamps look exactly identical and most of the power section except the ultralinear operation. The current amp just does not have the marshall "bite" to it and I think its because well the whole power section is different. What are some things to change to get closer to the tone I want

 

You have a High Fidelity tube amp vs a tube amp designed for a musical harmonic sound (Marshall). You might disconnect the ultralinear taps and re-bias the screen electrodes to change the grid/plate current curve of the output stage by eliminating the feedback effect on the beam optics. I'm not a musician so I would adjust the amp for the most accurate reproduction and adjust the input signal for the sound I want.
http://www.dos4ever.com/uTracer3/Schade.pdf
http://www.pmillett.com/file_downloads/ultralinear.pdf
http://www.tpub.com/neets/book6/21a.htm

 

You have a High Fidelity tube amp vs a tube amp designed for a musical harmonic sound (Marshall). You might disconnect the ultralinear tap and rebias the screen electrodes to change the grid/plate current curve of the output stage by eliminating the feedback effect on the beam optics. I'm not a musician so I would adjust the amp for the most accurate reproduction and adjust the input signal for the sound I want.
http://www.dos4ever.com/uTracer3/Schade.pdf
http://www.pmillett.com/file_downloads/ultralinear.pdf
http://www.tpub.com/neets/book6/21a.htm

So basically disconnect the ultralinear taps and use a resistor to get the screen grid current wh within limits. Run a wire off of point A to the screen grid on the tube with a resistor to get proper screen current I mean. Here's whats on the data sheet:
Rg2: 470
Ig2: 2x11.5 - 2X22.5 Whats with the weird multiplication? Why not just 23 to 45?
Vg2 max: 800

 

Bump. Can anyone verify what I said before?

How would I know what resistor value I am going to need? And once done how can I calculate screen current? (My usual method being Vdrop x transformer resistance. My current screen current is 36Ma.